<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        ul li{
            width: 100px;
            height: 100px;
            background-color: green;
            list-style-type: none;
            float: left;
            margin-left: 10px;
        }
    </style>
    <script src="jquery-1.12.2.js"></script>
    <script>
       $(function () {
           //页面加载后,让每个li的透明度发生改变
           //不同的元素不同的设置方式--each方法
           $("#uu>li").each(function (index,element) {
               //第一个参数是索引,第二个参数是对象
               //console.log(arguments[0]+"====="+arguments[1]);
               $(element).css("opacity",(index+1)/10);
           });
       });
    </script>

</head>
<body>
<ul id="uu">
    <li>1</li>
    <li>2</li>
    <li>3</li>
    <li>4</li>
    <li>5</li>
    <li>6</li>
    <li>7</li>
    <li>8</li>
    <li>9</li>
    <li>10</li>
</ul>
</body>
</html>